The present invention relates to rotators of the kind to be positioned between a crane hoisting boom and a lifting tool suspended in said boom and provided with hydraulic means intended to actuate the tool. In the rotator stand is mounted a vertical shaft which may be rotated by means of a motor, preferably supported by said stand. The shaft is provided with an upwardly extending prolongation portion which is enclosed in a sleeve and provided with two longitudinally extending bores through which pressurized medium may be supplied to and discharged from, respectively, the hydraulic means. Each bore has a lateral passageway debouching into its associated channel constituting a distribution chamber and collection chamber, respectively, for the pressurized medium.
The rotator is primarily intended for use in connection with a gripping tool which is operated by a hydraulic piston-and-cylinder unit and intended for loading lumber by means of lifting cranes onto loading vehicles. Rotators of this kind are exposed to extremely rough handling and considerable stress is exerted on the vertical shaft because of the frequent changes of the direction of rotation. Also the shaft bearings are exposed to heavy load. All these factors contribute to making it difficult to seal-off the pressurized medium at the points of the transitions between the stand and the shaft.